Room-temperature repositioning of individual C-60 molecules at Cu steps: Operation of a molecular counting device

C-60 molecules absorbed on a monoatomic Cu step have been reversibly repositioned st room temperature with the tip of a scanning tunneling microscope by performing controlled displacements along the step direction. We demonstrate the feasibility of building an abacus on the nanometer scale using single molecules as ''counters,'' Cu monoatomic steps as ''rods'' that constrain the molecular motion to one dimension, and the scanning tunneling microscope as an ''actuator'' for counting operations. (C) 1996 American Institute of Physics.